Evolution, Population Genetics, and Phylogeny Vocabulary

Comprehensive vocabulary flashcards covering macroevolution, population genetics, descent with modification, speciation, and phylogeny based on Campbell Biology in Focus Fourth Edition.

Macroevolution

Broad patterns of evolutionary change above the species level, including the emergence of major groups, origin of key adaptations, and the impacts of mass extinctions.

Strata

Sedimentary rock layers formed when new layers of sediment compress older ones, serving as a primary source of fossils.

Radiometric Dating

A method used to determine the absolute age of fossils based on the constant rate of decay of radioactive parent isotopes into daughter isotopes.

Half-Life

The time required for $50\%$ ($\frac{1}{2}$) of a radioactive parent isotope to decay into its daughter isotope.

Stromatolites

Layered rocks formed by prokaryotes that bound thin films of sediment together, representing Earth's oldest known fossils dating to $3.5\text{ billion years ago}$.

Heterochrony

An evolutionary change in the rate or timing of developmental events, altering body proportions and shape.

Paedomorphosis

An evolutionary alteration where reproductive development accelerates relative to nonreproductive development, causing a sexually mature adult to retain juvenile ancestral features.

Homeotic Genes

Master regulatory genes that determine the spatial organization and placement of body structures during embryonic development.

Hox Genes

A class of homeotic genes in animals that provide positional information during development, controlling where specific body structures form.

Exaptation

A feature or structure that originally evolved for one function but became co-opted to serve a different function in a new context.

Microevolution

Evolutionary change on its smallest scale, defined as a change in allele frequencies in a population over generations.

Phenotypic Plasticity

The ability of an individual genotype to produce different phenotypic traits when exposed to different environmental conditions.

Neutral Variation

Genetic variation that does not confer a selective advantage or disadvantage to an organism.

Gene Pool

The aggregate of all copies of every allele at every locus in all members of a population.

Fixed Allele

An allele for which only one state exists at a given locus in a population, rendering all individuals homozygous for that allele.

Hardy-Weinberg Equilibrium

The state of a non-evolving population where allele and genotype frequencies remain constant across generations, represented by $p + q = 1$ and $p^2 + 2pq + q^2 = 1$.

Genetic Drift

A process in which chance events cause unpredictable fluctuations in allele frequencies from one generation to the next, most markedly in small populations.

Founder Effect

A form of genetic drift occurring when a small number of individuals establish an isolated new population whose gene pool differs by chance from the source population.

Bottleneck Effect

A form of genetic drift resulting from a sudden, drastic reduction in population size, producing a surviving gene pool that may no longer represent the original population.

Gene Flow

The transfer of alleles into or out of a population due to the movement of fertile individuals or their gametes.

Relative Fitness

The contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals in the population.

Modes of Natural Selection

The three patterns by which natural selection alters phenotypic distributions: directional selection (favoring one extreme), disruptive selection (favoring both extremes), and stabilizing selection (favoring intermediate variants).

Directional Selection

Mode of natural selection in which conditions favor individuals at one extreme of a phenotypic range, shifting the population's phenotypic curve.

Disruptive Selection

Mode of natural selection in which conditions favor individuals at both extremes of a phenotypic range over individuals with intermediate phenotypes.

Stabilizing Selection

Mode of natural selection in which conditions favor intermediate phenotypes, acting against extreme phenotypic traits and reducing variation.

Balancing Selection

Natural selection that maintains stable frequencies of two or more phenotypic forms in a population's gene pool.

Heterozygote Advantage

A form of balancing selection in which individuals who are heterozygous at a specific gene locus have higher fitness than either homozygous phenotype.

Frequency-Dependent Selection

A form of balancing selection in which the fitness of a phenotype depends on how common or rare it is within the population.

Sexual Selection

A process of natural selection in which individuals with specific inherited characteristics are more likely than others to secure mates.

Sexual Dimorphism

Differences in secondary sexual characteristics between males and females of the same species, including size, color, ornamentation, or behavior.

Intrasexual Selection

Direct competition among individuals of one sex (usually males) for access to mates of the opposite sex.

Intersexual Selection

Selection in which individuals of one sex (usually females) are choosy in selecting their mates based on specific male traits.

Evolution

Descent with modification; the process by which lineages accumulate differences from their ancestors over time, or a change in a population's genetic composition across generations.

Scala Naturae

Aristotle's scale of nature concept, which organized unchanging species on a linear ladder of increasing complexity.

Binomial Nomenclature

The two-part Latin scientific naming format for species established by Carolus Linnaeus, consisting of the genus name followed by the specific epithet.

Paleontology

The scientific study of fossils, largely pioneered by French anatomist Georges Cuvier.

Use and Disuse

Lamarck's principle asserting that body parts extensively used become larger and stronger, while unused parts deteriorate.

Inheritance of Acquired Characteristics

Lamarck's hypothesis stating that structural modifications acquired during an individual's lifetime can be inherited by its offspring.

Adaptation

An inherited characteristic of an organism that enhances its survival and reproduction in a specific environment.

Artificial Selection

The selective breeding of domesticated plants and animals by humans over generations to promote desirable traits.

Homology

Similarity in underlying characteristics resulting from shared common ancestry.

Homologous Structures

Anatomical structures in different species that share structural similarity due to common ancestry, regardless of their current function.

Vestigial Structures

Remnants of historical features that performed important functions in an organism's ancestors but serve little or no current function.

Convergent Evolution

The independent evolution of similar functional features in distinct evolutionary lineages due to similar environmental pressures.

Analogous Features

Characteristics that share similar functions due to convergent evolution, lacking a shared evolutionary ancestor or origin.

Biogeography

The scientific study of the geographic distribution of biological species.

Endemic Species

Species of plants or animals that are native to a specific geographic area and found nowhere else in the world.

Speciation

The evolutionary process by which one ancestral species splits into two or more distinct descendant species.

Biological Species Concept

The definition of a species as a group of populations whose members can interbreed in nature to produce viable, fertile offspring, but cannot do so with other groups.

Hybrids

Offspring produced by interspecific mating between individuals belonging to two distinct species.

Prezygotic Barriers

Reproductive barriers that prevent fertilization by impeding mating attempts, preventing completion of mating, or hindering egg fertilization.

Postzygotic Barriers

Reproductive barriers that prevent a hybrid zygote from developing into a viable, fertile adult after fertilization occurs.

Habitat Isolation

A prezygotic barrier where two species occupy different habitats within the same area, causing them to rarely or never encounter each other.

Temporal Isolation

A prezygotic barrier where different species breed during different times of the day, different seasons, or different years.

Behavioral Isolation

A prezygotic barrier where unique courtship displays or specific species behaviors prevent interbreeding due to lack of mate recognition.

Mechanical Isolation

A prezygotic barrier where morphological or structural differences physically prevent successful mating completion.

Gametic Isolation

A prezygotic barrier where sperm of one species is biochemically or physiologically unable to fertilize the eggs of another species.

Reduced Hybrid Viability

A postzygotic barrier where genetic interactions between parent species impair the embryonic development or survival of the hybrid.

Reduced Hybrid Fertility

A postzygotic barrier where hybrid offspring develop into healthy adults but are sterile due to chromosomal differences that disrupt meiosis.

Hybrid Breakdown

A postzygotic barrier where first-generation hybrids are viable and fertile, but their second-generation offspring are feeble or sterile.

Morphological Species Concept

A species definition based on body shape, structural features, and visible physical traits.

Ecological Species Concept

A species definition based on the ecological niche and environmental interactions of a group of organisms.

Allopatric Speciation

The formation of new species resulting from geographic isolation and spatial separation of subpopulations.

Sympatric Speciation

The formation of new species within populations inhabiting the same geographic area without physical isolation.

Polyploidy

A condition in which an organism possesses extra sets of chromosomes due to errors during cell division.

Autopolyploid

An individual that possesses more than two chromosome sets derived entirely from a single parent species.

Allopolyploid

A fertile polyploid individual formed when two distinct species interbreed and combine their chromosome complements.

Hybrid Zone

A geographic region where members of different species meet and mate, producing offspring of mixed ancestry.

Reinforcement

The natural selection process strengthening prezygotic reproductive barriers in a hybrid zone because hybrid offspring are less fit than parent species.

Fusion

The weakening of reproductive barriers in a hybrid zone leading to substantial gene flow that merges two species back into one.

Stability (Hybrid Zone)

A outcome in a hybrid zone where hybrids continue to be produced reliably over time without reinforcement or fusion.

Punctuated Equilibria vs. Gradual Model

Two models for the tempo of speciation: (a) punctuated model, where species diverge in rapid bursts followed by long periods of stasis, and (b) gradual model, where species diverge slowly and continuously over long periods.

Punctuated Equilibria

A model of evolutionary history featuring long periods of apparent morphologic stasis punctuated by brief episodes of rapid speciation.

Phylogeny

The evolutionary history of a species or group of related species.

Systematics

An analytical discipline focused on classifying organisms and determining their evolutionary relationships.

Taxonomy

The scientific discipline concerned with naming and classifying organisms into a hierarchical system.

Taxon

A named taxonomic unit at any level of the Linnaean hierarchical classification system.

Phylogenetic Tree

A branching diagram representing a hypothesis about the evolutionary relationships among a group of taxa.

Sister Taxa

Groups of organisms that share an immediate common ancestor not shared by any other group, making them each other's closest relatives.

Rooted Tree

A phylogenetic tree that includes a branch point representing the most recent common ancestor of all taxa in the diagram.

Basal Taxon

A lineage that diverges early in the history of a group and lies near the common ancestor of the group.

Polytomy

A branch point in a phylogenetic tree from which more than two descendant groups emerge, signaling unresolved evolutionary relationships.

Cladistics

An approach to systematics that categorizes organisms into clades primarily based on common descent.

Clade

A group of species that includes an ancestral species and all of its descendants.

Monophyletic, Paraphyletic, and Polyphyletic Groups

Three group definitions in cladistics: (a) monophyletic group (clade) contains an ancestor and all descendants; (b) paraphyletic group contains an ancestor and some descendants; (c) polyphyletic group includes distantly related species without their common ancestor.

Monophyletic Group

A valid clade consisting of an ancestral species and all of its evolutionary descendants.

Paraphyletic Group

A group of organisms consisting of an ancestral species and some, but not all, of its descendants.

Polyphyletic Group

A group of organisms including distantly related species that lacks their most recent common ancestor.

Shared Ancestral Character

A character that originated in an ancestor of the taxon and is present in all members of the clade.

Shared Derived Character

An evolutionary novelty unique to a particular clade that is not found in its ancestral precursors.

Ingroup

The group of species whose evolutionary relationships are actively being investigated in a cladistic study.

Outgroup

A species or group closely related to the ingroup that diverged before them, used as a reference to determine ancestral versus derived states.

Maximum Parsimony

A principle stating that when evaluating phylogenetic hypotheses, the tree requiring the fewest evolutionary events or base changes is most likely correct.

Molecular Clock

A method for estimating the absolute time of evolutionary change based on the observation that specific genes evolve at constant rates.

Horizontal Gene Transfer

The transfer of genes between genomes of different species via plasmids, transposable elements, viral infection, or cellular fusion.